Im not sure if this is in the correct forum section but here goes because im also possibly after advice too ...

I am urgently looking for a decent used pc that i can use for photoshop editing and viewing the internet. One important thing is that it apparently it cant be dual core, my current pc is a dual core and has begun distorting colours in the dark areas of images when viewed on the internet.(when viewing Images on my pc they are fine)
This has been looked into an pc technician who told me the problem is caused by using my old dual core pc.
I am on quite a tight budget and dont know to much about computers so hoping someone on here can help.
Thanks in advance.

Build your own? It's easier than building lego! Have a look here for some ideas as to parts and pricing:-

https://www.reddit.com/r/PCMasterRace/wiki/builds

Oh, and if you follow the links to pc partpicker, you can change the currency in the top right corner by selecting the UK.

Thanks but it out of my price range and technical ability - i am hoping that someone has a decent used one i can buy.